/**
 * Ribbons Class File.
 * Creates low-poly ribbons background effect inside a target container.
 */
(function (name, factory)
{
    if (typeof window === "object")
    {
        window[name] = factory();
    }

})("Ribbons", function ()
{
    var _w = window,
    _b = document.body,//返回html dom中的body节点 即<body>
    _d = document.documentElement;//返回html dom中的root 节点 即<html>

    // random helper
    var random = function ()
    {
        if (arguments.length === 1) // only 1 argument
            {
                if (Array.isArray(arguments[0])) // extract index from array
                    {
                        var index = Math.round(random(0, arguments[0].length - 1));
                        return arguments[0][index];
                    }
                return random(0, arguments[0]); // assume numeric
            } else
        if (arguments.length === 2) // two arguments range
            {
                return Math.random() * (arguments[1] - arguments[0]) + arguments[0];
            }
        return 0; // default
    };

    // screen helper
    var screenInfo = function (e)
    {
        var width = Math.max(0, _w.innerWidth || _d.clientWidth || _b.clientWidth || 0),
        height = Math.max(0, _w.innerHeight || _d.clientHeight || _b.clientHeight || 0),
        scrollx = Math.max(0, _w.pageXOffset || _d.scrollLeft || _b.scrollLeft || 0) - (_d.clientLeft || 0),
        scrolly = Math.max(0, _w.pageYOffset || _d.scrollTop || _b.scrollTop || 0) - (_d.clientTop || 0);

        return {
            width: width,
            height: height,
            ratio: width / height,
            centerx: width / 2,
            centery: height / 2,
            scrollx: scrollx,
            scrolly: scrolly };

    };

    // mouse/input helper
    var mouseInfo = function (e)
    {
        var screen = screenInfo(e),
        mousex = e ? Math.max(0, e.pageX || e.clientX || 0) : 0,
        mousey = e ? Math.max(0, e.pageY || e.clientY || 0) : 0;

        return {
            mousex: mousex,
            mousey: mousey,
            centerx: mousex - screen.width / 2,
            centery: mousey - screen.height / 2 };

    };

    // point object
    var Point = function (x, y)
    {
        this.x = 0;
        this.y = 0;
        this.set(x, y);
    };
    Point.prototype = {
        constructor: Point,

        set: function (x, y)
        {
            this.x = x || 0;
            this.y = y || 0;
        },
        copy: function (point)
        {
            this.x = point.x || 0;
            this.y = point.y || 0;
            return this;
        },
        multiply: function (x, y)
        {
            this.x *= x || 1;
            this.y *= y || 1;
            return this;
        },
        divide: function (x, y)
        {
            this.x /= x || 1;
            this.y /= y || 1;
            return this;
        },
        add: function (x, y)
        {
            this.x += x || 0;
            this.y += y || 0;
            return this;
        },
        subtract: function (x, y)
        {
            this.x -= x || 0;
            this.y -= y || 0;
            return this;
        },
        clampX: function (min, max)
        {
            this.x = Math.max(min, Math.min(this.x, max));
            return this;
        },
        clampY: function (min, max)
        {
            this.y = Math.max(min, Math.min(this.y, max));
            return this;
        },
        flipX: function ()
        {
            this.x *= -1;
            return this;
        },
        flipY: function ()
        {
            this.y *= -1;
            return this;
        } };


    // class constructor
    var Factory = function (options)
    {
        this._canvas = null;
        this._context = null;
        this._sto = null;
        this._width = 0;
        this._height = 0;
        this._scroll = 0;
        this._ribbons = [];
        this._options = {
            // ribbon color HSL saturation amount
            colorSaturation: "80%",
            // ribbon color HSL brightness amount
            colorBrightness: "60%",
            // ribbon color opacity amount
            colorAlpha: 0.2,
            // how fast to cycle through colors in the HSL color space
            colorCycleSpeed: 6,
            // where to start from on the Y axis on each side (top|min, middle|center, bottom|max, random)
            verticalPosition: "center",
            // how fast to get to the other side of the screen
            horizontalSpeed: 200,
            // how many ribbons to keep on screen at any given time
            ribbonCount: 3,
            // add stroke along with ribbon fill colors
            strokeSize: 0,
            // move ribbons vertically by a factor on page scroll
            parallaxAmount: -0.5,
            // add animation effect to each ribbon section over time
            animateSections: true };

        this._onDraw = this._onDraw.bind(this);
        this._onResize = this._onResize.bind(this);
        this._onScroll = this._onScroll.bind(this);
        this.setOptions(options);
        this.init();
    };

    // class prototype
    Factory.prototype = {
        constructor: Factory,

        // Set and merge local options
        setOptions: function (options)
        {
            if (typeof options === "object")
            {
                for (var key in options)
                {
                    if (options.hasOwnProperty(key))
                    {
                        this._options[key] = options[key];
                    }
                }
            }
        },

        // Initialize the ribbons effect
        init: function ()
        {
            try
            {
                this._canvas = document.createElement("canvas");
                this._canvas.style["display"] = "block";
                this._canvas.style["position"] = "fixed";
                this._canvas.style["margin"] = "0";
                this._canvas.style["padding"] = "0";
                this._canvas.style["border"] = "0";
                this._canvas.style["outline"] = "0";
                this._canvas.style["left"] = "0";
               	this._canvas.style["top"] = "0";
               	this._canvas.style["width"] = "100%";
               	this._canvas.style["height"] = "100%";
                this._canvas.style["z-index"] = "0";
				// this._canvas.style["background-color"]="#1f1f1f";
                this._canvas.id = "bgCanvas";
                this._onResize();

                this._context = this._canvas.getContext("2d");
                this._context.clearRect(0, 0, this._width, this._height);
                this._context.globalAlpha = this._options.colorAlpha;

                window.addEventListener("resize", this._onResize);
                window.addEventListener("scroll", this._onScroll);
                document.body.appendChild(this._canvas);
            }
            catch (e) {
                console.warn("Canvas Context Error: " + e.toString());
                return;
            }
            this._onDraw();
        },

        // Create a new random ribbon and to the list
        addRibbon: function ()
        {
            // movement data
            var dir = Math.round(random(1, 9)) > 5 ? "right" : "left",
            stop = 1000,
            hide = 200,
            min = 0 - hide,
            max = this._width + hide,
            movex = 0,
            movey = 0,
            startx = dir === "right" ? min : max,
            starty = Math.round(random(0, this._height));

            // asjust starty based on options
            if (/^(top|min)$/i.test(this._options.verticalPosition))
            {
                starty = 0 + hide;
            } else
            if (/^(middle|center)$/i.test(this._options.verticalPosition))
            {
                starty = this._height / 2;
            } else
            if (/^(bottom|max)$/i.test(this._options.verticalPosition))
            {
                starty = this._height - hide;
            }

            // ribbon sections data
            var ribbon = [],
            point1 = new Point(startx, starty),
            point2 = new Point(startx, starty),
            point3 = null,
            color = Math.round(random(0, 360)),
            delay = 0;

            // buils ribbon sections
            while (true)
            {
                if (stop <= 0) break;stop--;

                movex = Math.round((Math.random() * 1 - 0.2) * this._options.horizontalSpeed);
                movey = Math.round((Math.random() * 1 - 0.5) * (this._height * 0.25));

                point3 = new Point();
                point3.copy(point2);

                if (dir === "right")
                {
                    point3.add(movex, movey);
                    if (point2.x >= max) break;
                } else
                if (dir === "left")
                {
                    point3.subtract(movex, movey);
                    if (point2.x <= min) break;
                }
                // point3.clampY( 0, this._height );

                ribbon.push({ // single ribbon section
                    point1: new Point(point1.x, point1.y),
                    point2: new Point(point2.x, point2.y),
                    point3: point3,
                    color: color,
                    delay: delay,
                    dir: dir,
                    alpha: 0,
                    phase: 0 });


                point1.copy(point2);
                point2.copy(point3);

                delay += 4;
                color += this._options.colorCycleSpeed;
            }
            this._ribbons.push(ribbon);
        },

        // Draw single section
        _drawRibbonSection: function (section)
        {
            if (section)
            {
                if (section.phase >= 1 && section.alpha <= 0)
                {
                    return true; // done
                }
                if (section.delay <= 0)
                {
                    section.phase += 0.02;
                    section.alpha = Math.sin(section.phase) * 1;
                    section.alpha = section.alpha <= 0 ? 0 : section.alpha;
                    section.alpha = section.alpha >= 1 ? 1 : section.alpha;

                    if (this._options.animateSections)
                    {
                        var mod = Math.sin(1 + section.phase * Math.PI / 2) * 0.1;

                        if (section.dir === "right")
                        {
                            section.point1.add(mod, 0);
                            section.point2.add(mod, 0);
                            section.point3.add(mod, 0);
                        } else {
                            section.point1.subtract(mod, 0);
                            section.point2.subtract(mod, 0);
                            section.point3.subtract(mod, 0);
                        }
                        section.point1.add(0, mod);
                        section.point2.add(0, mod);
                        section.point3.add(0, mod);
                    }
                } else
                {section.delay -= 0.5;}

                var s = this._options.colorSaturation,
                l = this._options.colorBrightness,
                c = "hsla(" + section.color + ", " + s + ", " + l + ", " + section.alpha + " )";

                this._context.save();

                if (this._options.parallaxAmount !== 0)
                {
                    this._context.translate(0, this._scroll * this._options.parallaxAmount);
                }
                this._context.beginPath();
                this._context.moveTo(section.point1.x, section.point1.y);
                this._context.lineTo(section.point2.x, section.point2.y);
                this._context.lineTo(section.point3.x, section.point3.y);
                this._context.fillStyle = c;
                this._context.fill();

                if (this._options.strokeSize > 0)
                {
                    this._context.lineWidth = this._options.strokeSize;
                    this._context.strokeStyle = c;
                    this._context.lineCap = "round";
                    this._context.stroke();
                }
                this._context.restore();
            }
            return false; // not done yet
        },

        // Draw ribbons
        _onDraw: function ()
        {
            // cleanup on ribbons list to rtemoved finished ribbons
            for (var i = 0, t = this._ribbons.length; i < t; ++i)
            {
                if (!this._ribbons[i])
                {
                    this._ribbons.splice(i, 1);
                }
            }

            // draw new ribbons
            this._context.clearRect(0, 0, this._width, this._height);

            for (var a = 0; a < this._ribbons.length; ++a) // single ribbon
            {
                var ribbon = this._ribbons[a],
                numSections = ribbon.length,
                numDone = 0;

                for (var b = 0; b < numSections; ++b) // ribbon section
                {
                    if (this._drawRibbonSection(ribbon[b]))
                    {
                        numDone++; // section done
                    }
                }
                if (numDone >= numSections) // ribbon done
                    {
                        this._ribbons[a] = null;
                    }
            }
            // maintain optional number of ribbons on canvas
            if (this._ribbons.length < this._options.ribbonCount)
            {
                this.addRibbon();
            }
            requestAnimationFrame(this._onDraw);
        },

        // Update container size info
        _onResize: function (e)
        {
            var screen = screenInfo(e);
            this._width = screen.width;
            this._height = screen.height;

            if (this._canvas)
            {
                this._canvas.width = this._width;
                this._canvas.height = this._height;

                if (this._context)
                {
                    this._context.globalAlpha = this._options.colorAlpha;
                }
            }
        },

        // Update container size info
        _onScroll: function (e)
        {
            var screen = screenInfo(e);
            this._scroll = screen.scrolly;
        } };
    // export
    return Factory;
});
new Ribbons();
